CHARACTERIZATION OF FERRIMAGNETIC PHASES FROM HYDROTHERMAL STORAGE OFCD NI/FE/AL-HYDROXIDES/

Ferrimagnetic phases formed from amorphous CdxNi1-xFe2-yAly(OH)(8) hyd roxides with y = 0, 0.2 and 0.4 in 0.2 steps for x, coprecipitated at pH 10 with NaOH from corresponding nitrates and stored one month at 15 0 degrees C in mother solution, were studied by XRD, IR, TG and magnet ic measurements The hydrothermally obtained spinel phases displayed th e same magnetic properties as the series sintered at 1000 degrees C on ly for y = 0.0 and 0.2. It is assumed that the highest incorporation o f Cd2+ ions into nickel ferrite occurs for x = 0.6-0.8. The comparison of the unit cell parameters with a standard straight a = f(x) line fo r the CdFe2O4-NiFe2O4 solid solutions sintered at 1000 degrees C, indi cates that the isomorphous incorporation of cadmium reaches about 0.4 mel. For the products obtained from precursors with nominal x = 1.0, t he formation of a solid solution between cadmium ferrite and maghemite has been assumed to justify the ferrimagnetism of samples. The first member of the solid solution series, NiFe2O4 (x = 0.0, y = 0.0) was us ed to prove that the hydrothermally obtained ferrites contain OH- grou ps substituting O2- ions in the spinel lattice.